Patent GB-922698-A (GB)
Title: Novel fibrous products
Inventor: ALLMAN WILLIAM THOMAS
IPC: D04H3/16
Filed: 1960-01-26
Abstract: A material readily convertible into tobaccosmoke filter plugs is made by extruding a liquid comprising an organic filament-forming material through a plurality of orifices into a gaseous atmosphere to effect solidification of the material in the form of a multiplicity of continuous filaments and rendering turbulent a zone in said atmosphere to cause random relative movement of the filaments, the random relative movement being of such violence that the filaments interlace to form a three-dimensional lace-like fibrous structure having appreciable strength across the direction of travel of the structure even in the absence of any substantial interfilamentary coalescence, the structure being removed from said zone at a linear speed sufficiently below that at which the liquid streams are extruded for the structure to have a denier of at least 40,000 and condensed into the form of a rope of cross-section suitable for forming <PICT:0922698/IV(a)/1> cigarette-plugs.  A solution of a filamentforming substance in a volatile solvent may be extruded into an evaporative atmosphere, e.g. a solution of cellulose acetate in acetone.  Other materials specified are ethyl cellulose, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate-formate, cellulose acetate-propionate, cellulose acetate-butyrate, polyamides, e.g. nylon 6 and nylon 66, linear polyesters, e.g. polyethylene terephthalate acrylonitrile polymers and copolymers, olefinic polymers, e.g. polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, polyvinylidene chloride.  Spinning solutions are preferably extruded under a pressure greater than 600 p.s.i.g., at linear rates of extrusion of 700 or more metres per minute, to produce filaments of individual denier less than 25, preferably less than 10 and the random relative movement of the filaments may be effected by causing jets of air to impinge on the filaments in the zone in which they are formed.  The lace-like product may be formed and withdrawn at a linear speed of less than one-tenth of the linear speed of extrusion, and preferably less than one twenty-fifth thereof, at such a rate in relation to the filament denier and number of filaments as to produce a rope having a total denier of 55,000-100,000.  The number of filaments may be 3,000 or more but is desirably less than 1,800.  Filaments so made have a rough crenulated surface, are irregularly crimped, have many lobes, discontinuous deep pits, folds, indentations, striations and knots and have an irregular crosssection.  Tobacco-smoke filter plugs are made from the rope so obtained by conventional methods.  Such a plug comprises a bundle of artificial filaments exhibiting no substantial interfilamentary coalescence, and of a total denier of at least 40,000 the severed ends of which filaments form opposite faces of the plug and the lengths of which follow such interlacing tortuous paths within the thickness of the plug that the latter resists forces tending to split it along all or substantially all planes joining said forces.  In apparatus as shown, spinnerets 45 are mounted at an angle of 45 degrees to a horizontal endless screen or perforated belt 46 driven at constant speed by rolls 47 and 48.  Air nozzle 50 discharges air at 90 degrees to the filaments which fall to the screen 46 as a web 52.  Hot air is supplied to the web via duct 58, and apertures 60, and leaves via duct 59.  Steam directed through nozzles 62 at web 52 reduces the vapour pressure of the spinning solvent and thus assists drying.  As the web 52 moves to the right it successively passes baffles 53, 54, leaves the cabinet, passes over guide 55 and H-bar 56, thus being formed into a rope which is pulled along by feed rolls 57 to be collected or directly formed into cigarette filters.